When is a varicella (chickenpox) booster dose recommended?

Varicella Booster Timing

All children should receive their second dose of varicella vaccine routinely at age 4-6 years (before entering prekindergarten, kindergarten, or first grade), with a minimum interval of 3 months after the first dose given at 12-15 months. 1, 2

Standard Two-Dose Schedule

First Dose

• Administer at 12-15 months of age as the routine primary vaccination 1, 2
• This timing aligns with MMR vaccine recommendations and limits the period when children lack varicella antibody 1

Second Dose (Booster)

• Routinely give at 4-6 years of age before school entry 1, 2
• This timing is strategically chosen because varicella incidence and outbreaks are higher among elementary school-aged children compared to preschool-aged children 2
• May be administered earlier if needed, provided the minimum 3-month interval is maintained 1, 2

Minimum Intervals Between Doses

Children 12 Months Through 12 Years

• Minimum interval: 3 months between first and second doses 1, 2, 3
• If the second dose is inadvertently given between 28 days and 3 months after the first dose, it is still considered valid and does not need to be repeated 2, 3
• The 3-month recommendation is based on the design of clinical studies evaluating two-dose efficacy in this age group 2, 3

Adolescents and Adults (≥13 Years)

• Minimum interval: 4 weeks (28 days) between doses 1, 2, 3
• Both doses should be single-antigen varicella vaccine, not MMRV 1, 3
• If more than 8 weeks elapse after the first dose, the second dose may be administered without restarting the schedule 1

Catch-Up Vaccination for Previously Unvaccinated or Partially Vaccinated Individuals

Children Who Received Only One Dose

• Second dose catch-up vaccination is specifically recommended for all children, adolescents, and adults who previously received only one dose 1, 3
• For children aged <12 years: minimum 3-month interval from first dose 1, 2, 3
• For persons aged ≥13 years: minimum 4-week interval from first dose 1, 2, 3
• The 11-12 year well-child visit should serve as an opportunity to evaluate vaccination status and administer catch-up doses 1, 3

Never-Vaccinated Individuals

• Children 12 months-12 years: begin two-dose series immediately, with second dose 3 months later 1, 2
• Persons ≥13 years: begin two-dose series immediately, with second dose 4-8 weeks later 1, 3

Rationale for Two-Dose Strategy

The two-dose recommendation addresses critical limitations of the single-dose program:

• Vaccine efficacy after two doses (98.3%) is significantly higher than after one dose (94.4%) 1, 2
• Recipients of two doses have a 3.3-fold lower risk of breakthrough varicella compared to one-dose recipients 1, 2
• After two doses, >99% of children achieve protective antibody levels compared to only 76-85% after a single dose 1, 2
• One-dose vaccination coverage of 99% has proven insufficient to prevent school outbreaks, as breakthrough varicella remains contagious 1, 4

Special Populations

Immunocompromised Patients

• Should receive varicella vaccine ≥4 weeks before initiating immunosuppressive therapy if immunocompetent at the time 1
• Use a 2-dose schedule separated by 3 months for children aged 1-12 years 1
• Use a 2-dose schedule separated by >4 weeks for persons aged ≥13 years 1
• Administer as single-antigen product only, not combined MMRV 1
• Highly immunocompromised patients should not receive varicella vaccine 1

School Entry Requirements

• All children entering school must have received two doses of varicella-containing vaccine or have other evidence of immunity 1, 2
• This requirement extends through all grade levels including college 1

Vaccine Formulation Selection

• MMRV vaccine (ProQuad): approved only for ages 12 months through 12 years 1, 2
• Single-antigen varicella vaccine (Varivax): approved for ages ≥12 months, required for persons ≥13 years 1, 2, 3
• When all components are indicated and not contraindicated, combination MMRV is preferred over separate injections for eligible children 1

Common Pitfalls to Avoid

• Do not use MMRV vaccine in persons ≥13 years—it is not licensed for this age group 1, 3
• Do not restart the vaccine series if the interval between doses is longer than recommended—simply give the second dose when the patient presents 1
• Do not delay the second dose unnecessarily—while longer intervals are acceptable, they should not be used as an excuse to postpone vaccination 2, 3
• Do not assume one dose is sufficient—even with 99% single-dose coverage, outbreaks continue to occur in schools 4